The present invention relates in general to an apparatus for mixing and dispensing of synthetic foams, and more particularly, to a mixing chamber for such apparatus which is adapted to be removably secured in operative association with the control means of such apparatus in a manner to be accessible from the outside of such apparatus for detachment therefrom.
As is well-known to those skilled in the art, the preparation of many synthetic foams, such as polyurethane foams, requires uniform mixing of liquid organic resins with polyisocyanates in a so-called mixing chamber. In this regard, it is often desirable to dispense the polyisocyanate resin mixture into a receptacle, such as a package or the like, before it is reacted to form the polyurethane foam, particularly when attempting to build up a foam structure around an object as in packaging. On particular problem associated with the handling of polyurethane foam is that the organic resin and polyisocyanate tend to react relatively rapidly, and can accumulate in the openings through which the organic resin and polyisocyanate are supplied to the mixing chamber. The accumulated foam in these openings are then most difficult to remove, generally requiring the disassembling of the apparatus for cleaning of the mixing chamber before continued use is possible.
It has been considered desirable, but never commercially feasible, to incorporate the dispensing apparatus in a system for packaging objects. In this regard, the dispensing apparatus would be located at one or more work stations overlying a conveyor belt and positioned in a downwardly-facing direction. Objects to be packaged would be indexed along the conveyor belt and subsequently stopped at each work station under the dispensing apparatus. The dispensing apparatus is activated to fill each receptacle with polyurethane foam so as to encapsulate the object therein. Because the openings in communication with the mixing chamber become obstructed with accumulations of polyurethane foam, the dispensing apparatus will generally become inoperable. In particular, the accumulation of foam therein will prevent the proper controlled flow of organic resin or polyisocyanate to the mixing chamber for production of suitable polyurethane foam. Once this condition has occurred, the dispensing apparatus must be disassembled and the mixing chamber cleaned prior to continued operation. As thus far described, the disassembling of the dispensing apparatus results in unnecessary system interruption and the associated loss of productivity and has thus made automated dispensing apparatus unfeasible.
In accordance with one known prior art dispensing apparatus, the mixing chamber is formed from a Teflon core having a bore longitudinally extending therethrough and a plurality of openings arranged therein in communication with the bore for supplying the organic resin and polyisocyanate thereto. A valving rod is slideably provided in interference fit within the bore to control the flow of organic resin and polyisocyanate from the openings into the bore and the subsequent discharge of the foam therefrom. Such interference fit between the valving rod and bore of the mixing chamber often results in the "cold forming" of the Teflon material forming such bore and openings therein. The cold forming of the Teflon material causes the loss of the interference fit resulting in the inability of the valving rod to effectively seal the openings to prevent the leakage of organic resin and polyisocyanate into the bore of the mixing chamber where they ultimately react to obstruct the mixing chamber with polyurethane foam, rendering the dispensing apparatus generally inoperable. Once this condition has occurred, the dispensing apparatus must be disassembled such that the mixing chamber can be replaced or rebuilt prior to continued operation of the dispensing apparatus.
Accordingly, it can be appreciated that there is a need for a dispensing apparatus which incorporates a mixing chamber which is readily detachable therefrom for replacement thereof with a minimum of system disruption and associated loss of productivity. Further, it can also be appreciated that there is a need for a mixing chamber incorporating a core constructed of Teflon or other such material which overcomes the associated problems with cold forming of such material during operation of the dispensing apparatus, i.e., loss of interference fit between the valving rod and bore of the mixing chamber.